The present invention relates to a method and apparatus for indicating the performance of the spectacle lens in a directly appreciable way.
As a methods for indicating spectacle lens performance indices, there have been known such methods as finding an average refractive power and astigmatism of the surface of the lens and indicating their distribution by contour lines on the surface of the lens.
However, the average refractive power and the astigmatism of a lens surface normally indicate only the performance of a curved surface of the lens and they are unable to directly indicate the performance of the lens in observing the outside world through the lens. The inventor has proposed an ocular optical system simulating method for simulating how things can be seen in observing the outside world through a spectacle lens as a method in which the performance of the lens in observing the outside world through the lens by the visual acuity of a person wearing the spectacle is taken into consideration. This method is a method of creating and using, not an optical image projected to the retinal surface of the eyes, but a rotation-based retinal image, defined as an image obtained by turning the eye-ball with respect to all object points within a visual field and by connecting images caught at the fovea. The rotational-based retinal image approximates an image perceived by the eyes through the spectacle lens.
The rotation-based retinal image and its motion video image can represent fluctuation, distortion and blur, which can be perceived in viewing the outside world through the spectacle lens. This method is described, for example, in U.S. patent application Ser. No. 09/415,498 filed Oct. 12, 1999, incorporated herein by reference. However, the rotation-based retinal image is a result in which the lens imaging performance is reflected on the image in viewing each physical point within the image and does not directly indicate the imaging performance itself. For instance, the rotation-based retinal image indicates the same result even if the point spread function (xe2x80x9cPSFxe2x80x9d) is different at a part of the image where changes in brightness are small. The rotation-based retinal image is unable to perfectly reflect a PSF whose extension is small in case of an original image having a smaller number of pixels.
The purpose of the invention is to provide a spectacle lens performance indicating method and apparatus, which can directly represent performance in observing the outside world through a spectacle lens.
In accordance with the above objects, the present invention provides a method for indicating spectacle lens performance. The method comprises the steps of (1) deriving a performance index indicating the performance of a spectacle lens at each of a plurality of object points within a visual field when the visual field is observed through the spectacle lens; and (2) displaying a scale of the performance index in a visually understandable mode.
In accordance with another embodiment of the present invention, there is provided method of indicating spectacle lens performance, comprising the steps of (1) deriving a performance index indicating the performance of a spectacle lens at each of a plurality of object points within a visual field when the visual field is observed through the spectacle lens; and (2) displaying a performance index distribution image of a visual field, which is created by determining a value of performance index for each pixel of the image corresponding to each object point within the visual field.
In a preferred embodiment, the image is selected from the group consisting of an original image, and a distorted original image. The step of displaying preferably comprises assigning a monochromatic luminosity to each said value of performance index.
In another embodiment, the step of displaying comprises assigning an RGB primary color luminosity to each said value of performance index.
In a further embodiment of the present invention, the step of deriving said performance index distribution image further comprises the steps of creating an original image, creating a distorted original image, creating a spectacle frame image, obtaining a performance index value, and creating a performance index distribution image. In this embodiment the first step is creating an original image within a visual field observed by an eye having a center of rotation and obtaining distances from each of a plurality of object points to said center of rotation, each said object point corresponding to a pixel in the original image. The second step is creating a distorted original image by using a ray tracing method to find a distortion of the visual field when viewed through said spectacle lens and obtaining a spectacle lens passing position of a ray emitted from each of said plurality of object points. The third step is creating a spectacle frame image indicating a position of a spectacle frame on one of said original image or said distorted original image by using the spectacle lens passing position data obtained in said distorted original image creating step. The fourth step is obtaining a performance index value corresponding to each of said plurality of object points for an optical system comprising said spectacle lens and an ocular model. The final step is creating a performance index distribution image by assigning a luminosity to each performance index value obtained in said performance index obtaining step and overlaying the spectacle frame mark image on the performance index distribution image.
Preferably, the luminosity is selected from the group consisting of a monochromatic luminosity, and an RGB primary color luminosity.
In a further embodiment of the method of the present invention, the first step is creating an original image including creating and placing virtual objects made by computer graphics in a virtual 3-D space, placing a center of rotation of an eye model at a specific position within the virtual 3-D space to create an image of the virtual objects within a visual field, which is a range within a specific pyramid having an apex located at said center of rotation and having a central axis along a specific visual line of sight, and measuring objective distances from each of said plurality of object points to said center of rotation. The second step in this embodiment is creating a distorted original image, including determining a central principal ray emitted from an object point at a center of the visual field and passing through a specific position of the spectacle lens, and determining a central ocular rotational direction by a ray tracing method, wherein a ray emitted from an object point, passing through a certain position of the spectacle lens and heading toward the center of rotation is defined as the principal ray and an exit direction of the principal ray from the rear surface of the spectacle lens is defined as the ocular rotational direction. The third step in this embodiment is determining, by a ray tracing method, a position, expressed as the ocular rotational direction to each object point, of each of said plurality of object points in an after-lens visual field having its central axis along the central ocular rotational direction. The fourth step in this embodiment is creating a distorted original image by using a ray tracing method to find a distortion of the visual field when seen through said spectacle lens and obtaining a spectacle lens passing position of a ray emitted from each of said plurality of object points. The fifth step in this embodiment is creating a spectacle frame image indicating a position of a spectacle frame on one of said original image or said distorted original image by using the spectacle lens passing position data obtained in said distorted original image creating step. The sixth step in this embodiment is deriving a performance index value, including providing an accommodation-dependent ocular optical system model as said ocular model and setting a power of accommodation of said ocular optical system model to an object point corresponding to each pixel of said original image or said distorted original image in accordance with a distance to the object point obtained in said original image creating step and the refractive power of the spectacle lens at the spectacle lens passing position of the principal ray obtained in said distorted original image creating step to obtain a spectacle lens performance index in a combined optical system of said spectacle lens and the ocular optical system model turned by the ocular rotational direction to said object point. The final step in this embodiment is creating a performance index distribution image including assigning a luminosity selected from a monochromatic luminosity and an RGB primary color luminosity corresponding to the performance index value of said spectacle lens for each pixel and of overlaying the spectacle frame mark image created in the spectacle frame image creating step on the performance index distribution image.
In yet another embodiment, the performance index is a residual average power error in viewing each object point. In a still further embodiment, the performance index is a residual astigmatism in viewing each object point. Another embodiment requires that the performance index be a deformation index indicating a degree of deformation in viewing each object point.
In a still further embodiment, the deformation index is derived by determining how a shape of a small circle centered at an object point changes when viewed through the spectacle lens, wherein the shape of the small circle is approximated to be an ellipse. The deformation index is preferably a ratio of major and minor axes of the ellipse.
In another embodiment, the performance index is a clearness index indicating a degree of blur in viewing each object point. The clearness index is preferably derived by determining a point spread function for each object point, approximating a spreading range of the point spread function as an ellipse, and defining the clearness index as half the diagonal length of a rectangle that circumscribes the ellipse.
Another embodiment of the method for indicating spectacle lens performance, comprising the steps of creating a movie story comprising a position of an eye, and a direction of a central visual line for a plurality of points in time; creating a spectacle lens performance index distribution image by a method according to one of the prior embodiments for each of the points in time in accordance with the movie story; and creating a motion video image with the spectacle lens performance index distribution images for the plurality of points in time.
A still further embodiment provides an apparatus for indicating spectacle lens performance. The apparatus comprises means for deriving a performance index indicating the performance of a spectacle lens at each of a plurality of object points within a visual field when the visual field is observed through the spectacle lens. The apparatus also comprises means for displaying a performance index distribution image of a visual field, which is created by determining a value of performance index for each pixel of the image corresponding to each object point within the visual field.
The means for deriving a performance index further comprise a number of additional means, including means for creating an original image including creating and placing virtual objects made by computer graphics in a virtual 3-D space, placing a center of rotation of an eye model at a specific position within the virtual 3-D space to create an image of the virtual objects within a visual field, which is a range within a specific pyramid having an apex located at said center of rotation and having a central axis along a specific visual line, and measuring objective distances from each of said plurality of object points to said center of rotation. The means for deriving performance index also comprise means for creating a distorted original image including determining a central principal ray emitted from an object point at a center of the visual field and passing through a specific position of the spectacle lens, and determining a central ocular rotational direction by a ray tracing method, wherein a ray emitted from an object point, passing through a certain position of the spectacle lens and heading toward the center of rotation is defined as the principal ray and an exit direction of the principal ray from the rear surface of the spectacle lens is defined as the ocular rotational direction. In addition, the performance index deriving means comprises means for determining, by a ray tracing method, a position, expressed as the ocular rotational direction to each object point, of each of said plurality of object points in an after-lens visual field having its central axis along the central ocular rotational direction. The performance index deriving means also comprises means for creating a distorted original image by using a ray tracing method to find a distortion of the visual field when seen through said spectacle lens and obtaining a spectacle lens passing position of a ray emitted from each of said plurality of object points. Also included are means for creating a spectacle frame image indicating a position of a spectacle frame on one of said original image or said distorted original image by using the spectacle lens passing position data obtained by said distorted original image creating means. Additionally, there are provided means for deriving a performance index value including providing an accommodation-dependent ocular optical system model as said ocular model and setting a power of accommodation of said ocular optical system model to an object point corresponding to each pixel of said original image or said distorted original image in accordance with a distance to the object point obtained in said original image creating step and the refractive power of the spectacle lens at the spectacle lens passing position of the principal ray obtained in said distorted original image creating step to obtain a spectacle lens performance index in a combined optical system of said spectacle lens and the ocular optical system model turned by the ocular rotational direction to said object point. And, lastly, there are provided means for creating a performance index distribution image including assigning a luminosity selected from a monochromatic luminosity and an RGB primary color luminosity corresponding to the performance index value of said spectacle lens for each pixel and of overlaying the spectacle frame mark image created in the spectacle frame image creating means on the performance index distribution image.
Lastly, in a further embodiment of the apparatus according to the invention there is provided means for creating a movie story comprising a position of an eye, and a direction of a central visual line for a plurality of points in time; means for creating a spectacle lens performance index distribution image for each of the points in time in accordance with the movie story; and means for creating a motion video image with the spectacle lens performance index distribution images for the plurality of points in time.
Further objects, features and advantages of the present invention will become apparent from the Detailed Description of the Preferred Embodiments, which follows, when considered together with the attached figures.